Browsing by Author "Carvalho, V."
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- Green chemistry and biorefineries: common future?Publication . Carvalho, V.; Relvas, F.; Lopes, André; Morais, Ana Rita C.; Silva, Sara P. Magalhães da; Mata, Ana C.; Roseiro, Luisa B.; Lukasik, Rafal M.Green Chemistry and Biorefinery concepts are two approaches helping to develop new and more sustainable processes.The implementation of both methodologies impels to fossil-independent future with bioeconomy based on natural feedstock like biowaste and industrial by-products. The development of technologies for valorisation of these resources is a key role of society in the creation of sustainable and more environmentally friendly future. Shortly after the Rio Declaration on Environment and Development, Anastas and Warner presented 12 Principles of Green Chemistry but more a decade before Trevor Kletz in his Jubilee lecture entitled “What you don’t have, can’t leak” draw the frames in which scientific and industrial work should be performed. This basis of green chemistry created a fundament for further development and implementation of Anastas and Warner principles of green chemistry. One of these frames is integration of green chemistry principles in the biorefinery concept. The biorefinery is an industrial facility (or network of facilities) that cover an extensive range of combined technologies aiming to full sustainable transformation of biomass into their building blocks with the concomitant production of biofuels, energy, chemicals and materials, preferably of value added products. One of the principles of green chemistry is the use of more sustainable solvents. Some examples of them are ionic liquids (ILs) and supercritical fluids (scF). This work will demonstrate the successful examples of lignocellulosic biomass valorisation using green solvents answering the question regarding the feasibility of future biorefineries made in a greener manner.
- Relevance of the acidic 1-butyl-3-methylimidazolium hydrogen sulphate ionic liquid in the selective catalysis of biomass hemicellulose fractionPublication . Carvalho, V.; Lopes, André; Lukasik, Rafal M.The ability of acidic 1-butyl-3-methylimidazolium hydrogen sulphate ionic liquid (IL) to hydrolyse and to convert wheat straw into pivot compounds without additional catalyst was scrutinised. The pre-treatment with this IL allowed to obtain a liquor rich in hemicellulosic sugars, furans and organic acids, and a solid fraction constituted mainly by cellulose and lignin. Pre-treatment conditions, such as temperature and residence time were set to produce xylose or furfural at fixed 1/10 (w/w) biomass/IL ratio and 1.24 % (w/w) water content in the pre-treatment process. Statistical modelling based on Doehlert experimental design was applied to establish optimal conditions to produce xylose and furfural. Temperature demonstrated to have greater effect on the production of xylose, rather than time of pre-treatment, and it is significantly incisive on furfural formation as well. To compare the reaction conditions, the severity factor for studied IL was proposed and applied in this work. Furthermore, water was verified to have a large influence on the equilibrium of the hemicellulose hydrolysis. The increase of the water content close to 10 % (w/w) in the system disfavour xylose dehydration and thus allows increasing significantly the production of hemicellulose-derived monosaccharides. At last, an important disclosure in the reaction of biomass with [bmim][HSO4] is the formation of humins for high severity pre-treatments.